1. Technical Field
The present invention relates generally to the production of a puff extrudate and, specifically, to an improved process of producing a plurality of similarly shaped curly puff extrudate pieces from a single curly puff extrudate.
2. Description of Related Art
The production in the prior art of a puff extruded product, such as snacks produced and marketed under the Cheetos™ brand label, typically involves extruding a corn meal or other dough through a die having a small orifice at extremely high pressure. The dough flashes or puffs as it exits the small orifice, thereby forming a puff extrudate. The typical ingredients for the starting dough may be, for example, corn meal of 41 pounds per cubic foot bulk density and 12 to 13.5% water content by weight. However, the starting dough can be based primarily on wheat flour, rice flour, soy isolate, soy concentrates, any other cereal flours, protein flour, or fortified flour, along with additives that might include lecithin, oil, salt, sugar, vitamin mix, soluble fibers, and insoluble fibers. The mix typically comprises a particle size of 100 to 1200 microns.
The puff extrusion process is illustrated in FIG. 1, which is a schematic cross-section of a die 12 having a small diameter exit orifice 14. In manufacturing a corn-based puff product, corn meal is added to, typically, a single (i.e., American Extrusion, Wenger, Maddox) or twin (i.e., Wenger, Clextral, Buhler) screw-type extruder such as a model X 25 manufactured by Wenger or BC45 manufactured by Clextral of the United States and France, respectively. Using a Cheetos like example, water is added to the corn meal while in the extruder, which is operated at a screw speed of 100 to 1000 RPM, in order to bring the overall water content of the meal up to 15% to 18%. The meal becomes a viscous melt 10 as it approaches the die 12 and is then forced through a very small opening or orifice 14 in the die 12. The diameter of the orifice 14 typically ranges between 2.0 mm and 12.0 mm for a corn meal formulation at conventional moisture content, throughput rate, and desired extrudate rod diameter or shape. However, the orifice diameter might be substantially smaller or larger for other types of extrudate materials.
While inside this orifice 14, the viscous melt 10 is subjected to high pressure and temperature, such as 600 to 3000 psi and approximately 400° F. Consequently, while inside the orifice 14, the viscous melt 10 exhibits a plastic melt phenomenon wherein the fluidity of the melt 10 increases as it flows through the die 12.
It can be seen that as the extrudate 16 exits the orifice 14, it rapidly expands, cools, and very quickly goes from the plastic melt stage to a glass transition stage, becoming a relatively rigid structure, referred to as a “rod” shape if cylindrical, puff extrudate. This rigid rod structure can then be cut into small pieces, further cooked by, for example, frying, and seasoned as required.
Any number of individual dies 12 can be combined on an extruder face in order to maximize the total throughput on any one extruder. For example, when using the twin screw extruder and corn meal formulation described above, a typical throughput for a twin extruder having multiple dies is 2,200 lbs., a relatively high volume production of extrudate per hour, although higher throughput rates can be achieved by both single and twin screw extruders. At this throughput rate, the velocity of the extrudate as it exits the die 12 is typically in the range of 1000 to 4000 feet per minute, but is dependent on the extruder throughput, screw speed, orifice diameter, number of orifices and pressure profile.
As can be seen from FIG. 1, the snack food product produced by such process is necessarily a linear extrusion which, even when cut, results in a linear product. Consumer studies have indicated that a product having a similar texture and flavor presented in a “curl,” “spiral,” or “coil spring” shape (all of which terms are used synonymously by Applicant herein) would be desirable. An example of such spiral shape of such extrudate is illustrated in FIG. 2, which is a perspective view of one embodiment of a spiral or curl shaped puff extrudate 20. The apparatus for making curly puff extrudate is the subject matter of U.S. pat. No. 6,722,873 entitled “Apparatus and Method for Producing a Curly Puff Extrudate” and is incorporated herein by reference.
Curly puff extrudate 20 has proven difficult to cut into smaller, more manageable extrudate pieces. Some type of containment vessel such as a pipe or tube (terms used synonymously by the Applicant herein) is used for the curly puff extrudate production and a cutting device at the end of the tube results in surging and plugging within the tube, particularly during start-up and shutdown of the extruder. FIG. 3 illustrates a perspective view of a device involving a number of tubes 30 attached to a die face 18. The exit end of each tube 30 is attached to an extruder face 23. This arrangement then permits the attachment to the extruder face 23 of a circular cutting apparatus 24 having a number of individual cutting blades 26. Such an arrangement is shown with ten tubes 30 connected to a die face 18. Although not shown in FIG. 3, the tube 30 and extruder face 23 configuration can be designed such that the dies 12 are allowed to vent until specific conditions are met (such as extrudate bulk density, specific mechanical energy, moisture content, screw speed, and die pressure), then the tube 30 can be rotated over the dies 12 by device of an additional rotatable plate (not shown) between the tubes 30 and the dies 12.
However, cutting the curly puff extrudate 20 at the end of the tube 30 in a multiple tube 30 assembly is not preferable because the cutting blades 26 drag the curly puff extrudate 20 from one tube 30 to another which results in jagged and non-uniform ends of individual curly puff extrudate 20 pieces. FIG. 4 is an example of a piece of curly puff extrudate 20 cut with a device similar to the one in FIG. 3. Additionally, when the curly puff extrudate 20 is produced in a multiple tube assembly, the tubes may not produce extrudate at the same rate, so a single cutter cutting multiple tubes will produce curly puff extrudate pieces of differing lengths.
This problem can be overcome by completely severing the extrudate at the die face when it is in the plastic melt state rather than the glass transition state. However, severing the extrudate at the die face disconnects the individual extrudate pieces and it is sometimes preferable to keep the extrudate connected for processing before separating the extrudate into individual extrudate pieces. Examples of processing include: conveying, seasoning, stretching, separating, or confining the extrudate in a containment vessel. Therefore, a need exists for an effective method of cutting the extrudate in the plastic melt state without completely separating the extrudate
Another problem with the apparatus in FIG. 3 is that it does not allow for the release of steam and other hot gasses released from the expanding extrudate. The steam and other gasses promote surging and plugging within the tube. Therefore, a need also exists for an apparatus and method for venting steam and other hot gasses so they cannot enter the containment device.
It should be understood that while a need exist for an apparatus capable of cutting a curly puff extrudate without plugging a containment tube, the need is not limited to curly puff extrudate. A need also exists for an apparatus for cutting a sinusoidal puff extrudate as well as other types of linear and non-linear puffed extrudates.
Consequently, a need exists for an apparatus and method of cutting the puff extrudate into smaller puff extrudate pieces that will create smooth cuts at each end of the individual pieces. A need also exists for an apparatus and method that will prevent plugging of the tube during start-up, operation, and shutdown of the extruder. A need further exists for a method of releasing steam from the expanding extrudate. Moreover, a need exists for an apparatus and method of controlling the length of the individually cut puff extrudate pieces in a configuration with multiple orifices for each die.